Pruritus, or itching, is an extremely uncomfortable condition that can cause problems during the course of daily life. Pruritus is caused by various factors, including skin diseases such as atopic dermatitis, senile pruritus, urticaria, eczema, insect bites, dry skin or rashes, kidney disease, diabetes, collagen diseases, aging, and heat and cold stimuli. There are also cases in which scratching a pruritic site may lead to a vicious cycle in the form of further exacerbating symptoms or causing more intense itching.
For example, atopic dermatitis is known to be easily exacerbated by external stimuli such as perspiration, scratching or rubbing, and itching is the most important treatment objective.
Thus, it is important to provide treatment that first suppresses itching in order to treat the skin diseases as listed above.
Various medicinal and topical treatment methods are known for the treatment of pruritus. Examples of the medicinal treatment methods include the use of antihistamines such as diphenhydramine, chlorpheniramine maleate, mectazine, ketotifen, azelastine, oxatomide, terfenadine or epinastine, and antiallergic agents such as tranilast or suplatast. Examples of the topical treatment methods include the use of moisturizers such as vaseline, urea or heparin, antihistamines such as diphenhydramine or chlorpheniramine maleate, steroids such as dexamethazone or hydrocortisone, antipruritic agents such as crotamiton, and local anesthetics such as dibucaine or lidocaine.
With respect to acacia, acacia honey is known, and tannin which is extracted from bark thereof is known to be able to be used as a tanning agent or a wood adhesive, while more recently, extracts of genus Acacia have been disclosed to have selective inhibitory effects on COX-2 (Patent Document 1), and bark of genus Acacia has been disclosed to have active oxygen eliminating effects (Patent Document 2) and skin whitening effects due to the effect of inhibiting tyrosinase activity (Patent Document 3). However, acacia bark and polyphenols derived from acacia bark have heretofore not been known to have any antipruritic effects.
[Patent Document 1] JP2004-532811A
[Patent Document 2] JP2004-352639A
[Patent Document 3] JP10-025238A